1. Field of the Invention
The present invention relates to a novel copying machine, more particularly to a copying machine which is free from any drawback concomitant with copying machines according to the prior art, which has its performance remarkably improved and which has such additional functions as have failed to be incorporated in copying machines according to the prior art.
2. Description of the Prior Art
A copying machine has been developed from the era of the so-called "limited number of copies", in which the copying operation using salts of silver or diazo formed the principal trend, to the era of the so-called "great number of copies", in which there is used a copying machine called an electrophotographic copying machine using electrophotography having such a high degree of completeness as a general business copying machine that it can enjoy the following advantages: that copies can be instantly obtained; that the copying speed is high; that the storability of the copies is excellent; that originals are not selected; and that usual paper can be used.
The electrophotographic copying machine is able to have high completeness and marketability and is widely used as the main source of the copying machine because it not only the uses the copying process which was invented by Carlson in 1938, but also because of the subsequent developments of the materials such as photosensitive materials or developing agents, the process such as a charging, developing or transferring process, and the practical marketing techniques.
An electrophotographic copying machine is constructed by the method which will be described hereinafter. The electrophotographic copying machine is characterized by using means such as an insulating photoconductive member for the photosensitive member which has an insulating property capable of holding electrostatic charges in the dark, which can receive electric charges and which is rendered electrically conductive when exposed to a light. First of all, in the dark, a corona charger, in which a thin wire called a corona wire and made of tungsten is extended under tension along a grounded plate, for example, is used to apply a high voltage between the wire and the conductive base of the photosensitive member so that the surface of this photosensitive member is wholly charged with a positive or negative polarity to provide it with photosensitiveity. Then, an optical image corresponding to the picture image of an original is focused on the aforementioned photosensitive member, thus charged by means of an optical system which is composed of a light source, a lens and a reflecting mirror, so that the charges are placed upon the surface of the photosensitive member in accordance with the quantity of the irradiating light, thereby to convert the optical image of the picture image of the original into an electrostatic image.
The electrostatic image thus formed on the photosensitive member is developed and visualized by the well known electrophotographic development.
Now, the conventional copying machine thus far described is widely used but has various drawbacks and functional limits, as follows:
The optical system is complex and requires a large space so that problems arise in the compactness and cost of the copying machine, in case a copy board is fixed to improve the operability.
If the sensitivity of the photosensitive meaner is increased with a view to increasing the copying speed, the reduction in the image density for a continuously copying operation and the establishment of fog are liable to take place so that the picture image becomes instable.
Upon production of the photosensitive member, on the other hand, the desired characteristics are liable to disappear, and the yield is deteriorated to raise the cost.
It is difficult to preset the process condition for improving or stabilizing the picture image.
The conventional copying machine is a single-function machine having nothing but a copying function, and it is difficult to provide hybrid functions including that of recording the signal from a communication line in addition to the copying function.